Radar altimeters on TOPEX/Poseidon, Jason-1, Jason-2, Jason-3, and Sentinel-6 Michael Freilich have provided a global mean sea level record since 1992, showing a rise of about 3.3 millimeters per year and roughly 10 centimeters over 30 years. Arctic summer sea ice extent has declined by about 12% per decade since the 1980s, with the Arctic…
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DGNSS improves GNSS accuracy by using stationary reference receivers to broadcast corrections to rovers, transforming standalone GPS accuracy from about 5–15 m to sub-meter or centimeter levels, with SBAS like WAAS (USA) and EGNOS (Europe) delivering about 1–3 m for aviation. Real-Time Kinematic (RTK) uses carrier-phase measurements and double-differencing to fix integer ambiguities, delivering centimeter-level…
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GPS III, first launched in 2018, delivers three times the accuracy and eight times the anti-jamming performance of previous GPS generations, with a GPS III satellite named Katherine Johnson launched by SpaceX in 2025. GPS modernization includes the L1C common civil signal for interoperability with Galileo and a Next Generation OCX ground system to handle…
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GSSAP-1 and GSSAP-2 were launched on July 28, 2014 aboard a Delta IV M+(4,2) from Cape Canaveral, accompanied by the ANGELS experimental satellite. The GSSAP satellites operate in near-geosynchronous orbit roughly 35,900 km (22,300 miles) above Earth and function as a “neighborhood watch” for the GEO belt, providing space situational awareness to USSPACECOM. Built by…
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Geostationary orbit sits at about 35,786 km above the equator and completes a sidereal day (~23h56m), so satellites appear fixed over one longitude; Arthur C. Clarke popularized it in 1945, giving the region the nickname the Clarke Belt. A GEO satellite remains stationary relative to the ground, allowing ground antennas to point at a fixed…
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The United States operates the Advanced Extremely High Frequency (AEHF) constellation, delivering jam-resistant, global, protected military communications including nuclear command and control links. Navstar GPS is a 31-satellite global navigation system that provides precise positioning, navigation, and timing to guide munitions such as JDAM and to synchronize encrypted networks. Defense Support Program (DSP) and the…
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By late 2022, more than 10,000 aircraft worldwide were equipped with in-flight connectivity, and about 65% of airlines planned further IFC investments in the next few years. Aireon’s space-based ADS-B payloads on Iridium NEXT have been operational since 2019, enabling global real-time tracking and supporting ICAO’s 15-minute GADSS position reporting standard. COSPAS-SARSAT, a global satellite…
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L-band MSS terminals, such as Inmarsat FleetBroadband and Iridium Certus, provide global coverage with compact antennas but limited data throughput. Ku-band VSAT (12–18 GHz) has been the maritime workhorse, Ka-band HTS (26–40 GHz) offers higher capacity, while C-band deployments are restricted near shore due to interference and large dish requirements. GEO satellites offer broad coverage…
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Iridium operates 66 active LEO satellites in a cross-linked constellation, providing truly global coverage including the poles. Inmarsat uses 3–4 GEO satellites at about 36,000 km altitude to cover most of the globe from roughly 70°N to 70°S, and its IsatPhone 2 offers 8 hours of talk time. Globalstar runs about 48 LEO satellites to…
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Cambodia has over 22 million cellular subscriptions in a population of about 17 million, yielding a mobile penetration of roughly 131.5% due to multiple SIM ownership. As of early 2023, fixed internet subscriptions were about 310,000 nationwide, underscoring a mobile-first connectivity pattern. Cambodia’s first submarine cable, the Malaysia-Cambodia-Thailand link, landed in 2017, and a Hong…
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